The present invention relates to anionic starting materials/surfactants, particularly those which are prepared from the direct esterification of fatty acids and isethionate (i.e., directly esterified fatty acyl isethionate or xe2x80x9cDEFIxe2x80x9d) and which may be used in personal wash compositions such as, for example, personal wash bars or personal wash shower gel compositions. Specifically, the invention relates to compositions comprising mixtures of DEFI and modified DEFI compounds. The modified DEFI compounds are compounds made in the same DEFI reactor where DEFI is made (from reaction of fatty acid and isethionate) except that the fatty acid is substituted and reacted with isethionate and/or the isethionate is substituted and reacted with fatty acid. As noted, the mixtures may also comprise compounds where the fatty acid substitute and isethionate substitute may react with each other.
In personal wash compositions (e.g., bars or liquids), one very common anionic surfactant which is used is acyl isethionate. This compound is milder than soap, yet retains characteristics which consumers associate with good cleaning (e.g., foaming). It would be greatly beneficial to find compounds which are still milder and/or less drying than fatty acid isethionates, while maintaining good foaming profiles. Further, when used in bar preparation, such compounds should be suitable for bar processing conditions.
The acyl isethionate surfactant is commonly produced by the direct esterification of a fatty acid (e.g., C10 to C16 fatty acid such as lauric fatty acid) and isethionate (e.g., OHCH2CH2SO3xe2x88x92Na+) in a process commonly known as the xe2x80x9cDEFIxe2x80x9d process (process for making directly esterified fatty acid isethionate). The DEFI process is conducted in a single DEFI reactor.
Applicants have now discovered that, if either the fatty acid starting component is partially replaced (e.g., with silicone based carboxylic acids, fatty acids derived from Neem oil or castor oil of varying chain distribution, dicarboxylic acids, etc.); and/or the isethionate starting component is partially replaced (e.g., with glycerol, sorbitol, pentaerythritol, amines etc.), not only will the DEFI reactor form the expected directly esterified fatty acid isethionate (from the fatty acid and isethionate which are not partially replaced), but a portion of the final reaction component will also represent combinations of, for example, isethionates modified by the different types of fatty acids (when the standard fatty acid is partially replaced), or alcohol esters or amides (when the isethionate is partially replaced). The cosurfactants produced during the production of the main active (e.g., sodium lauroyl or sodium cocoyl isethionate) are mild and result in milder surfactant mixtures.
That is, the same DEFI reactor will produce mixtures of xe2x80x9cstandardxe2x80x9d fatty acid isethionate and these xe2x80x9cmodifiedxe2x80x9d DEFI compounds. Applicants are aware of no prior art which teaches or suggests that mixtures of standard and modified DEFI can be produced in the same reactor, let alone that at least some of these mixtures may provide enhanced mildness without sacrificing foaming. It should be noted that a small part of the mixture may also comprise compounds formed by fatty acid replacement reacting with isethionate replacement.
U.S. Pat. No. 5,300,666 to Imperante et al., teaches a process for condensing silicone carboxylates with sodium isethionate under conditions similar to the xe2x80x9cDEFIxe2x80x9d process (the reaction time of the reference is 5-15 hours versus 90 minutes for standard DEFI reaction; same temperatures of 220-240) to produce high foaming, mild surfactants. This reaction, however produces only a single xe2x80x9cmodifiedxe2x80x9d DEFI compound. It does not produce mixtures of xe2x80x9cstandardxe2x80x9d and modified DEFI in a single reactor. Further, it teaches only the replacement of standard (e.g., lauric) fatty acid with a silicone based carboxylic acid and fails to teach or suggest the many other possible fatty acid replacements of the subject invention. It also fails to teach that the isethionate portion may be replaced instead of or, in addition to the fatty acid portion. Finally, the process involves longer reaction times than those of the subject invention, 5 to 15 hours versus 90 minutes.
Other references also teach compounds which could be the xe2x80x9cmodifiedxe2x80x9d DEFI component of the subject invention. U.S. Pat. No. 4,476,055 to Du Vernet, for example, teaches C21 dicarboxylic acid isethionates as anionic surfactants; Schmidt et al., in xe2x80x9cA Novel Dianionic Surfactant from the Reaction of C14-Alkenylsuccinic Anhydric with Sodium Isethionatexe2x80x9d, JAOCS, 71 (7):695-703 (1994) teach an isethionate reacted with C14alkenyl succinic acid; and Bistline et al., in xe2x80x9cSurface Active Agents from Isopropenyl Esters: Acylation of Isethionic Acid and N-Methyltaurinexe2x80x9d, JAOCS 48 (11): 657-60 (1971) teach another isethionate based surfactant made using DEFI-like conditions (e.g. high temperature and acidic catalysts).
Other references teach isethionate-based surfactants made under high temperature and basic catalysts (see, e.g., DE 4,337,035 to Henkel (1995); DE 4,315,810 to Henkel (1994); DE 1,234,708 to General Aniline and Corp. (1967); U.S. Pat. No. 5,296,627 to Tang et al. (assigned to PPG Industries) or JP 04,360,863 to Tosoh Corp. (1992)).
Again, none of these references teach or suggest mixtures of standard DEFI with the modified DEFI produced in the same reactor by at least partially replacing the standard fatty acid and/or isethionate. Further, none of these references teach or suggest that such mixtures may be milder than DEFI alone while maintaining a strong foaming profile.
Suddenly and unexpectedly, applicants have discovered new compositions wherein said compositions comprise mixtures of xe2x80x9cstandardxe2x80x9d DEFI (made from reaction of isethionate with C8 to C22 straight chain substantially saturated (preferably greater than 85% saturated) monocarboxylic fatty acids (it should be noted that in mixtures such as xe2x80x9ccocoxe2x80x9d fatty acid, there may be some small percentage of unsaturated fatty acid such as, for example, oleic fatty acid) and DEFIs which have been modified by partially replacing (1-80%, preferably 10-50%, most preferably 10-35%) the fatty acid and/or the isethionate in the reactor so that the replacing material reacts with the fatty acid or isethionate to produce the modified DEFI.
More specifically, the compositions comprise mixtures of:
(a) xe2x80x9cstandardxe2x80x9d DEFI (Isethionate reacted with C8-C22, preferably C10-C16 straight chain substantially saturated non-carboxylic acid); and
(b) a DEFI produced by either reacting C8-C22 fatty acid with a replacement polyol (e.g., glycerol, sorbitol, pentaerythritol or almost any compound with available OH group), organic acid, or amine or mixtures thereof; or reacting isethionate with a replacement fatty acid (e.g., silicone based carboxylic acid, multicarboxylic fatty acid derived from Neem oil or castor oil of varying chain distribution, dicarboxylic acids).
In a second embodiment of the invention, the invention comprises a process for making a mixture of xe2x80x9cstandardxe2x80x9d DEFI and xe2x80x9cmodifiedxe2x80x9d DEFI in a single reactor which process comprises: mixing:
(i) about 20 to 50% by wt., preferably 25% to 40% by wt., alkali metal isethionate;
(ii) about 35% to 75% by wt., preferably 45% to 65% by wt. C8-C22 straight chain fatty acid;
(iii) about 0 to 20% by wt., preferably 0.1 to 18% by wt. replacement for alkali metal isethionate; and
(iv) about 0% to 10% by wt., preferably 0.1 to 9% by wt. replacement for C8-C22 straight chain fatty acid;
at a temperature of 180 to 240xc2x0 C.
wherein an acid catalyst is used; (e.g., zinc oxide, zinc isethionate, or any Lewis acid);
wherein (i) and (ii) and at least one of (iii) or (iv) must be mixed in the reactor.
It should be noted that xe2x80x9creplacementxe2x80x9d reactants may be combined at the beginning of the reaction or that they may be used at some point after compounds (i) and (ii) have been reacting for awhile (e.g., 5 minutes to 60 minutes).
The present invention relates to compositions comprising mixtures of (1) xe2x80x9cstandardxe2x80x9d directly esterified fatty acid (xe2x80x9cDEFIxe2x80x9d) and (2) either (a) product formed from reaction of isethionate and a xe2x80x9creplacementxe2x80x9d for fatty acid normally used during production of alkali metal ester of C8-C22 substantially saturated, straight chain monocarboxylic acid fatty or (b) product formed from the reaction of the substantially saturated, straight chain monocarboxylic acid and a xe2x80x9creplacementxe2x80x9d for isethionate (e.g., alcohols, organic acids, amines etc.).
Specifically, mixtures of standard xe2x80x9cDEFIxe2x80x9d (1) and the cosurfactants produced by 2(a) or 2(b) above have been found to enhance mildness (as measured by decreased zein solubilization) while maintaining adequate foaming. Further, the mixtures are produced in a single reactor.
More specifically, a standard xe2x80x9cDEFIxe2x80x9d reaction is defined as the mixture of a C8-C22, generally C10 to C16 fatty acid (e.g., lauric acid or coco fatty acid) with alkali metal isethionate as follows: 
Normally, reaction is conducted at ratio of about 1 to 1 to 2 to 1 fatty acid to isethionate using 0.001-0.05, preferably 0.01 to 0.04 of total reactants by weight of a catalyst (e.g., zinc oxide, zinc isethionate or any Lewis acid including sulfuric acid, p-toluene sulfonic acid, sodium bisulfite etc.) at a temperature of about 150xc2x0 C. to 250xc2x0 C., preferably about 200xc2x0 C. to 250xc2x0 C. for about 1 to 3 hours.
Both in the xe2x80x9ctypicalxe2x80x9d DEFI process and in that of the invention, it is possible to use a little bit of the final product (after made or obtained once) and use this as an emulsifying agent for the reaction. This helps speed up the reaction.
The components of the reaction may be added in any order and, although yields may be better reacting one agent before another, any order of addition is contemplated.
The directly esterified fatty acyl isethionate (xe2x80x9cDEFIxe2x80x9d) formed from this reaction has reasonable mildness properties (as measured by zein solubilization) and good foaming ability (e.g., about 95-100 mls foam in a 100 milliliter graduated cylinder when using about 5% solution).
Typically, the subject invention involves the xe2x80x9creplacementxe2x80x9d of a portion of one of the two reactants (e.g., sodium isethionate) with, for example in the case of isethionate replacement or modification, alcohol, organic acid or mixtures thereof. Thus, typically, for example, one quarter by weight of the isethionate may be replaced by a 2:1 ratio of glycerol and lactic acid mixture (in reaction with lauric acid, for example) resulting in a final mixture comprising sodium lauroyl isethionate ester, left over lauric acid, left over sodium isethionate in addition to some glycerol monolaurate (from reaction of lauric acid and glycerol) and glycerol monolaurate monolactate.
It is these typical mixtures which have then been analyzed to determine mildness (typically more mild as measured by zein compared to if no isethionate had been replaced) and foaming (typically slightly less foaming, but still adequate).
Replacement/Modification for Isethionate
Typical replacements for the isethionate reactant under standard reaction conditions (e.g., using same catalysts as for DEFI reaction, same perspective ranges, i.e., 150 to 250xc2x0 C., preferably 200 to 250xc2x0 C. and same reaction times, i.e., 1 to 3 hours) are polyols, organic acids, amines and mixtures thereof).
Examples of alcohols include any straight or branched chain, cyclic or acyclic molecule containing two or more hydroxy groups (where the position of the hydroxy groups is not critical) such as glycerol, ethylene glycol (example of a 1,2 diol), propylene glycol (example of a 1, 3 diol), meso-erythritol, pentaerythritol, and the like, reduced sugars, such as sorbitol, mannitol, and the like or sugars, preferably pentoses and hexoses, mono or disaccharides, such as glucose, galactose, xylose,lactose, maltose or mixtures thereof.
Examples of organic acid replacement for Isethionate include linear, branched or cyclic compounds containing a hydroxy group alpha or beta to a free carboxylic acid moiety. These include alpha or beta hydroxy acids such as glycolic acid, lactic acid citric acid, salicylic acid, and the like and mixtures thereof.
Examples of amines which may be used to partially replace isethionate include any linear, branched or cyclic compound containing at least one NH2 or NH group. Such compounds include taurine, N-methyl taurine, tris-hydroxyaminomethane, tris-hydroxyaminoethane; amino acids such as glysine, lysine, and the like, hydroxyamines and polyhydroxyamines, such as N, N diethanolamine, N-methyl glucamine, sorbitol amine, and the like; and mixtures thereof.
Typically, anywhere from 5% to 75%, preferably 5% to 50%, more preferably 5% to 20% of the isethionate, on a weight basis, will be replaced so that both isethionate ester and replacement active are formed in the same reactor.
Replacemen/Modification of C8-C22 Standard, Unbranched, Substantially Saturated Monocarboxylic Acid
In addition to (or in place of) partially replacing isethionate, it is also possible to replace the standard C8 to C22 straight chained, substantially saturated monocarboxylic acid normally used in the DEFI process.
The fatty acid replacement may be:
(1) any triglyceride derived from plant, animal or vegetable sources (for use in transesterification or transamidation process); or
(2) any linear, straight, branched, or cyclic compound, saturated and/or partially unsaturated compound containing one or more free carboxylic acid moieties.
Examples of fatty acid replacements include compounds containing such carboxylic acid moiety derived from plant, animal or vegetable source (e.g., fatty acids derived from tallow fat, Neem and/or caster oil).
Also included are heteroatom containing compounds, such as ethoxylated fatty acids (e.g., Neodol(copyright) surfactants sold by Shell) and silicone based carboxylic acids and the like, such as those described by Imperatore (U.S. Pat. No. 5,300,666) sold/manufactured by Dow corning and Siltech Inc. and prepared by the reaction of any polymer with a terminal silanic hydrogen with a terminal vinyl containing carboxy compound and polycarboxylic acids, (such as dicarboxylic acids including adipic acid, azeleic acid, suberic acid, sebacic acid, 1, 12 dodecanedicarboxylic acid, 1, 14 tetradecanedicarboxylic acid, C21 dicarboxylic acid such as described in U.S. Pat. No. 4, 476,055, and the like).
Other compounds which may be fatty acid replacements are substituted acids and/or anhydrides, such as those prepared via the condensation of alpha-olefins with maleic acid and succinic acid (these are produced by Shell as described in JAOCS 71(7) 695-703 (1994) in xe2x80x9cA Novel dianionic surfactant from the reaction of C14 alkenyl succinic anhydride with sodium isethionatexe2x80x9d); and alpha-sulfo fatty acids such as those described by Hung in J. Ind. Chem. 15(3) 317-21 (1987). Both references are incorporated by reference into the subject application.
Among the multiple carboxylic acid replacements which can be used are dicarboxylic such as adipic acid, and 1, 12 dodecanedicarboxylic acid.
Compositions of the invention will have foam values as measured by defined protocol of about 40 and higher, preferably about 50 milliliters mls and higher, more preferably 50 to about 230. It should be understood that foaming values are to some extent dependent on the size of vessel used to generate foam but that, in general, good foam values were always seen.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts or ratios of materials or conditions or reaction, physical properties of materials and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d.
Where used in the specification, the term xe2x80x9ccomprisingxe2x80x9d is intended to include the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more features, integers, steps, components or groups thereof.